???...hmm...
If it is not 7dtd i can hardly help directly, because i did not use this Utility outside of this game, but maybe this will give you an idea:
you should be warned how resources .resS work
https://7daystodie.com/forums/showthread.php?22675-Unity-Assets-Bundle-Extractor&p=488856&viewfull=1#post488856
https://7daystodie.com/forums/showthread.php?22675-Unity-Assets-Bundle-Extractor&p=502817&viewfull=1#post502817
here is a method where you can make an offset and specify a different data location -
https://7daystodie.com/forums/showthread.php?32600-Overriding-vanilla-files-(assets-)&p=314195&viewfull=1#post314195
By the way, the added resources in the asset are just there and they are not included in the header, the list by which the program can know that it is there.
And just remember that there may be separate header files like "globalgamemanagers" that may contain paths for files from other bundles.
PS: perhaps you are asking how to make the created file have a path in the resource....yes so can be done...it's possible and i did ... but i forgot as, if I recall write here....
PPS: oh yes - but this is same...
https://7daystodie.com/forums/showthread.php?22675-Unity-Assets-Bundle-Extractor&p=492165&viewfull=1#post492165